Lapping machine



July 21, 1931.

S. HOLT LAPPING MACHINE Filed Sept. 30. 1930 WI mass gwuwntoz SAMUELHOLT Patented July 21, 1931 PATENT OFFICE- SAMUEL HOLT, OF RIDGEWOOD,NEW YORK, ASSIGNOR '10 NORTON COMPANY, OF WORCESTER, MASSACHUSETTS, ACORPORATION OF MASSACHUSETTS LAPPING 'MACHIN E Application filedSeptember 30, 1930. Serial No. 485,464. I

F This invention relates to improvements in lapping machines andespecially to a lap ping element for such machines which tends to wearunevenly.

Heretofore, it has been common practice to perform a mechanical lappingoperation by mounting several work pieces within a guiding cage movablypositioned between two parallel opposed lapping surfaces, and

to eccentri'cally rotating said work cage and laps relatively, therebycausing the work pieces to go through a series of irregular motionswhile in engagement with said laps. One familar type of lap for such amachine comprises an annular metal ring or disk which has its flatoperative surface charged with abrasive grains. I In lapping certaintypes of work, there is often an uneven wear upon the operative lappingsurface, especially when lapping long narrow work pieces,

which results in the lap surface becoming conical or otherwise misshapedso that it no longer lies in a single plane. Any uneven wear upon thelap causes a corresponding unevenness upon the work pieces and thusresults in imperfect work. When a work piece is revolved by the rotatingwork cage oversuch a surface, a much faster abrading action will oftenoccur at the outer periphery of the annulus than at its inner periphery,

since the portion of the work engaging the outer periphery moves over alarger diameter during the sametime interval that the work moves overtheinner periphery and at a relatively greater speed. This faster abradingaction over such portions of the lap creates an uneven wear thereuponand is apt to cause corresponding inaccuracies in the work,necessitating frequent truing operations which involve a considerableloss of time and expense. Since a metal lap of this type may only becharged with abrasive grains at its working surface, it must necessarilybe recharged after every truing operation, which involves a furtherexpense and loss of operating time of the machine.

The object of this invention is to provide a lapping member which is soconstructed that as it wears away. compensation for uneven wear may beeffected to make themtire lapping surface lie in a true plane, thereyincreasing the period of active service of the lap as well as theproductivity of the machine.

With this and other objects in view, as will be apparent in thefollowing disclosure, my invention resides in the combination of parts iset forth in the specification and covered by a. lapping head before anywear has occurred to cause the operative lapping surface to be out oftrue;

Fig. 2 is a similar view, but showing the lapping element deformed tocompensate for its uneven wear; i

Fig. 3 is a. horizontal section on theline 3-3 of Fig. 1 showing a planview. of the lapping head; and

Fig. 4 is a vertical elevation, partly broken away, of a lapping machineembodying the invent-ion.

In accordance with my invention, I have provided a lapping machine,which may be of the type shown in the patent to Inclge No.

1,610,527, comprising two parallel opposed lapping members and a workpositioning cage interposed therebetween, said laps and cage beingrelatively rotatable to cause a lapping operation. The two opposed lapshave their active abrading surfaces arranged preferably in parallelplanes and they may be an nular in form and mounted concentrically oneabove the other. One of the lapping members, or both, is so constructedthat it may be deformed to compensate for any uneven wear upon the lapsurface which has resulted in an out-of-plane condition, and therebycause the active abrading surface to lie entirely'within the same plane.To this end, I may make thelap in two parts, a lapping element and asupporting head, one of which is fulcrumed on the other and preferablyadjacent that periphery where the- ,greater" wear occurs so that theelement may be deformed to correct its out of true condition. I alsoprovide means for deforming the Worn element to move the portion of itsubjected to the lesser wear so as to return its abrading surface tosuch a position that the whole surface lies in substantially the sameplane.

Referring to the drawings, I have therein shown one specific form of myinvention especially adapted for lapping long pieces of Work, althoughit may be utilized to lap various types of flat and cylindrical workwith equal success. Referring to Fig. 4, I have there shown a lappingmachine of the type described in the Indge patent which comprises tWoopposed upper and lower lapping members 10 and 12 with a Work cage 13interposed therebetween for carrying a plurality of work pieces 14, oneof said members and the cage being relatively rotatable to produce alapping operation.

It has been found that a circular lap does not usually wear evenly buttends to approach a, conical surface, especially when long narrow workpieces are moved along its peripheral surface during the lapping action,owing to the fact that the portion of the work contacting with the outerportion of a Hat circular lap is subjected to a greater abrading actionthan that portion of the work contacting with the inner lap peripheryduring the same abrading period. To overcome this difliculty and savethe necessity of very frequent and expensive truing and rechargingoperations, I have provided a means-whereby the lapping element may besprung or flexedback to a single lapping plane as the lap becomes worn.To accomplish this, I make the lap in two parts, one being a supportinghead 15 and the other a thin deformable metal lapping element 16 chargedwith abrasive grains at its abrading surface 17 The lapping head 15 issupported from a spider member 18 by means of suitable screws 19. Thespider 18 is affixed to the end'of a shaft 21 by a key 22 and a nut 24screwed onto a threaded portion 25 of the shaft. The shaft 21 may bearranged for vertical movement to move the upper lap toward and from thework and also for rotation if it is desired to rotate the lap relativeto the work.

The lower face of the annular lapping head 15 is beveled'to provide aperipherally raised edge 32 which may serve as a fulcrum about which theoperator may flex the annular lapping element 16. The inner portion ofthe element is secured to the head 15 by means of spaced tension screws29 which are freely mounted in the head 15 and threaded into the element16 and located close to the inner peripheries of the concentric lappinghead and element. After the portion of the lapping element adjacent toits outer periphery has worn to a detrimental. extent, the operator taryfulcrum in place of the raised edge 32 on the beveled portion of thehead.

The same type of lapping member may be equally well applied to the lowerlaps as indicated in Fig. 4, and the construction of the parts will beas above described. In this figure, the lower lap 12 is mounted on arotatable support 34 which is driven by means of a power rotated sleeve35, and the cage 13 is eccentrically rotated by a member 36, as fullydescribed in said patent.

The operation and utility of the device will be readily apparent fromthe above description. By means of this construction, I have increasedthe life of the lap and the productivity of the machine as well asinsured accuracy of operation for producing a large number of pieces ofwork.

Having thus described my inventlon, What I claim as new and desire tosecure by Letters Patent is:

l. A lapping machine comprismg two opposed lapping members and a workcage interposed therebetween, one of which 1s rotatable relative to theother to cause a lapping action, said lapping members havmg theiroperative faces in parallelism, and means to deform one of said membersafter it has been worn out of true to again bring its operative surfaceinto a true and accurate lapping plane.

2. A lapping machine comprising two opposed lapping members and a workcage 1nterposed therebetween which are relatively rotatable to cause ala ping action, one of said lapping members eing composed of asupporting head and a'lapping element, and means for adjustably securingthe lapping element to the head and for deforming the element tocompensate for uneven wear upon its abrading surface and so bring theentire lapping surface within the same plane.

3. A lapping machine comprising two opposed lapping members and a workcage interposed therebetween which are relatively rotatable to perform alapping operation, one

operative surface lie within the same plane.

4. A lapping device comprising a supporting member and a lapping elementmovably secured thereto and means to flex the lapping clement wherebythe active lapping surface may be deformed to compensate for any unevenWear and thereby bring said surface back into the same plane.

5. A lapping device comprising a support ing member and a lappingelement removably secured thereto, means fulcruming the lapping elementupon the periphery of the supporting member and means for flexing theinner portion of the lapping element to compensate for uneven Wear uponthe lapping surface to bring said surface Within the same plane.

6. A lapping device comprising a supporting member and an annular lapplng element removably secured thereto, means fulcruming the lappingelement adjacent to the periphery of the supporting member and spacedclamping screws securing thelapping element to the supporting member ata distance remote from the fulcrum which may serve to flex the innerportion of said element and return its operative face to a sin lelapping plane and thereby compensate %or any uneven wear thereon.

N. Y., this 3rd day Signed at Brooklyn, of Sept., 1930.

SAMUEL HOLE.

